A machine is known for the precision shaving of tooth flanks of a toothed workpiece from copending application Ser. No. 129 769 filed Mar. 12, 1980. Because of its type of design it is suited for the manufacture of spherical (crowned) or conical tooth flanks. The tool carrier which carries out the feed movement is on the one side suspended tiltably about a horizontal axis and on the other side guided on a fixed part through an adjustably inclined swivel guide bar. Depending on the inclination of the swivel guide bar, the tool carrier and thus the tool is inclined during feeding and at the same time carries out a feed movement toward the workpiece.
As a rule the plane of rotation of the tool is directed toward the axial center of the workpiece. In the case of wide workpieces it is often desired to enlarge, at least toward the end of the feed the inclined position, namely the camber of the tool or, however, to reduce the mentioned feed movement, for example, to obtain a wider pressure surface on the tooth flanks. This is easily possible with suitably curved swivel guide bars. However, such curved swivel guide bars are expensive to manufacture and require in addition special developments on the grooved pivot member which guides them.
Therefore, a resultant purpose of the present invention is to provide a simpler control correcting device for spherical crowned shaving and similar precision-working methods, which can be applied to the known machine.
The objects and purposes of the invention are met by providing a means for cancelling a portion of the feed movement of the tool toward the workpiece, wherein the reduction of feed movement depends on the tilting movement of a guide carrier which supports the tool carrier for longitudinal feeding of the tool along the workpiece surface.
In a further development of the invention, an eccentric pivot pin pivotally supports the guide carrier and thus the tool for pivoting with respect to one axis of such eccentric pivot pin, whereas an eccentric lever is responsive to longitudinal movement of the tool with respect to the guide carriage for causing such eccentric lever to rotate the eccentric pivot bolt and thereby raise the guide carriage and tool independent of the direction in which longitudinal tool movement occurs. Thus, the tool can be provided with a curved path along the tooth to be machined on the workpiece. The tool at any point along such curved path is perpendicular to or at any different desired angle to the workpiece tooth to be machined. The amount of such reduction in the feed movement of the tool toward the workpiece can be changed by changing of the means driving the eccentric lever, e.g., means such as cams or a template of shape depending on the desired finished shape of the workpiece tooth, which cams or templates can be manufactured more easily than providing a swivel guide bar which is curved in two directions.
The means for correcting, or partial cancelling, of tool feed movement toward the workpiece can if desired be rendered ineffective by supporting the eccentric lever such that the cams or template are not effective to vary the motion of the eccentric lever.
Workpieces with conical or spherical-conical (crowned conical) teeth have not been capable of being worked on a machine of the aforementioned type having a straight swivel guide bar. Accordingly, the basic purpose of the invention is broad enough to encompass a structure which permits the working of such teeth. To this end, an arm which projects from the tool carrier, and which carries the swivel guide bar, is made adjustable in length. A change in such length of arm results in an inclined position of the tool carrier and thus also of the guide carrier supporting the latter. Longitudinal movement of the tool carrier thereby is inclined to the workpiece axis in correspondence to the desired conicity of the workpiece tooth to be formed. In this mode the aforementioned cams and template are not needed.
Furthermore, in order to be able to produce spherical-conical teeth, a control lever connects through a steering link to the guide carrier, with the distance between the hinge point of the steering link on the control lever and the bearing surface of the eccentric lever on the camming means being adjustable. The adjustability of the steering link can be carried out by making the steering link adjustable in length between its two hinge points, by adjusting the location of the hinge point of the steering link on the guide carrier, or by employing an adjustable bar on the eccentric lever to engage the cams. In order to obtain spherical-conical teeth, the guide carrier or the tool carrier must be positioned so as to be inclined to its initial position. At the same time, however, it is necessary for the eccentric lever to be positioned parallel to the control lever, which carries the cams or template, in order to provide the conical teeth as a result of the aforementioned inclined positioning and to also crown such teeth in correspondence to the position of the cams or form of the template.